1. Field of the Invention
The present invention relates to method for manufacturing a sheet glass formed by heating and extending a glass preform and method for manufacturing a glass substrate using the sheet glass.
2. Description of the Related Art
Conventionally, substrates of semiconductor elements, spacers used for field-effect-type flat panel displays or glass sheets used for magnetic disc substrates etc. require better thickness uniformness or surface roughness.
As a method of manufacturing a sheet glass having predetermined thickness and improved surface roughness, a method etc. of heating and softening a glass preform and extending it into a desirable thickness of sheet glass has been proposed (see Japanese Laid-open Patent Publication No. H11-199255).